Internal combustion engines typically utilize one of several methods and/or devices to vary valve lift profiles, including roller finger followers.
Switchable roller finger followers are known, see, for example, U.S. Pat. No. 7,174,869 and DE 10 2006 046 573 A1. Such finger followers have an outer lever pivotably mounted outside an inner lever and a roller rotatably mounted on a transverse axle in a slot in the inner lever. The top surface of the outer lever acts as a contact surface for a high lift cam and the top surface of the roller acts as a contact surface for a low lift cam. A coupling element, which typically includes shuttle pin and a coil spring, is mounted at one end of the finger and oil from an oil source is used to activate the coupling element. When the coupling element is activated, it locks the outer lever to the inner lever and requires the follower to follow both the high lift cam and the low lift cam. When the coupling element is deactivated, the outer lever is free to pivot and, under the aid of a torsion spring, the outer lever pivots freely in conjunction with the high lift cam. This movement by the outer lever is conventionally referred to as the lost motion stroke.
Conventionally, the coil spring of the coupling element is mounted inside of, or in line with, the shuttle pin. However, packaging a coil spring in the housing of the finger follower that has a proper rate and diameter between the shuttle pin and the roller is very challenging.